| Title: | Volcano topography, structure and intrinsic attenuation: their relative influences on a simulated 3D visco-elastic wavefield
|
| Authors: | O'Brien G.S. and Bean C.J., 2009 |
| Abstract: | The seismic wavefield recorded on volcanoes can be significantly influenced by path effects. Scattering from
the topography and internal volcanic structure can play a dominant role in the recorded seismograms.
Intrinsic attenuation is also thought to play an important role in the characteristics of volcano seismic signals.
We use 3D numerical modelling of wave propagation in elastic and visco-elastic media including complex
velocity models and topography to investigate the scattering and attenuation characteristics of synthetic
seismograms. We generate 5 distinct volcano models and simulate wave propagation through these models
using shallow and deep double-couple broadband sources. We then analyse 129 synthetic seismograms
calculated on the free surface. The synthetic seismograms resemble VT-A and VT-B events. The scattering
effect of the topography alone is capable of producing complex seismograms. The introduction of an internal
velocity structure increases the duration of these seismograms while the introduction of intrinsic attenuation
decreases the duration but not the complexity.We fitted our synthetic seismograms to the diffusion in a halfspace
model to quantify the scattering and attenuation coefficients. The scattering quality factor measured on
all 129 stations for all 5 volcano models was similar. Therefore, we deduce that the topography appears to be
the dominant scatterer. The intrinsic attenuation quality factor for each of the specific models cannot be
accurately recovered using the diffusion in a half-space model. The measured quality factor is not only
sensitive to the attenuation properties but also to the structural properties. In all cases the scattering is more
dominant than the intrinsic attenuation. |
| ICHEC Project: | Seismic source modelling and wave propagation in volcanoes |
| Publication: | Journal of Volcanology and Geothermal Research (2009) 183:122-136 |
| URL: | http://dx.doi.org/10.1016/j.jvolgeores.2009.03.004 |
| Keywords: | diffusive wavefield; intrinsic attenuation; volcano structure topography; numerical simulations |
| Status: | Published |
